Image input device for generating a video signal for an image reproduction apparatus

Abstract

An image input device for imaging an object includes a process circuit which has a negative/positive inversion function for forming a luminance signal and color difference signals to reproduce a negative image from pixel signals corresponding to the object or for forming the luminance signal and the color difference signals to reproduce a positive image from the pixel signals corresponding to the object. An image of the object may be reproduced in the image input device as a video signal in a blue-back mode by a blue-back circuit. The blue-back circuit processes the luminance signal and the color difference signals so that a portion of the object is forcibly colored blue or a family color when the level of the luminance signal outputted from the process circuit is within a predetermined range. Also, the blue-back circuit processes the luminance signal and the color difference signals so that a high brightness portion of the object is forcibly set to a white level or a family color when the level of the luminance signal outputted from the process circuit exceeds the predetermined range. As a result, the image object may be reproduced in the blue-back mode so that an illegible object can be displayed as a legible document.

What is claimed is: 
     
       1. An image input device, comprising: image pickup means for developing a pixel signal of an object as first, second and third color pixel signals;   pixel signal processing means for passing through said first, second and third color pixel signals unchanged when a normal positive color image display mode or a blue-back display of a negative image mode is selected by an operator and inverting said first, second and third color pixel signals when a negative color image display mode or a blue-back display of a positive image mode is selected by an operator;   a matrix circuit for developing a luminance signal and first and second color difference signals from said first, second and third color pixel signals outputted by said pixel signal processing means;   blue-back processing means for passing through said luminance and first and second color difference signals unchanged when said normal positive color image display mode or said negative color image display mode is selected by an operator and inverting said luminance signal, changing said first color difference signal to a ground signal and changing said second color difference signal to a predetermined voltage signal when said blue-back display of a positive image mode is selected by an operator, said blue-back processing means comprises an inverter for inverting said luminance signal, a switch for changing said first color difference signal to said ground signal and a predetermined voltage source for changing said second color difference signal to said predetermined voltage signal in said blue-back display of positive and negative image modes and first, second and third display mode switches for simultaneously switching said luminance and first and second color difference signals between said normal positive color image display mode and said negative color image display mode to said blue-back display of positive and negative image modes; and   an encoder for developing a video signal from said luminance signal and said first and second color difference signals outputted by said blue-back processing means.   
     
     
       2. An image input device according to claim 5, wherein said image pickup means comprises an optical system for focusing on said object, a color image pickup device for reading out said pixel signal of said object in synchronism with a dot-sequence scanning timing by a predetermined drive and a pre-amplifier for amplifying said pixel signal from said color image pickup device. 
     
     
       3. An image input device according to claim 5, wherein said first color pixel signal comprises a red pixel signal, said second color pixel signal comprises a blue pixel signal and said third color pixel signal comprises a green pixel signal. 
     
     
       4. An image input device according to claim 3, wherein said first color difference signal comprises an R - Y color difference signal and said second color difference signal comprises an B - Y color difference signal. 
     
     
       5. An image input device according to claim 3, wherein said color image pickup device comprises a CCD solid state device. 
     
     
       6. An image input device according to claim 3, wherein said color image pickup device comprises a MOS solid state device. 
     
     
       7. An image input device according to claim 1, wherein said pixel signal processing means comprises first, second and third buffers for passing through said first, second and third color pixel signals respectively when said normal positive color image display mode or said blue-back display of a negative image mode is selected by an operator, first, second and third inverters for inverting said first, second and third color pixel signals respectively when said negative color image display mode or said blue-back display of a positive image mode is selected, first, second and third image reproduction switches for simultaneously switching between said normal positive and negative color image display modes and first, second and third γ correcting circuits for performing a γ correction on said first, second and third color pixel signals outputted from said first, second and third buffers or said first, second and third inverters respectively in response to said first, second and third image reproduction switches. 
     
     
       8. An image input device, comprising: image pickup means for developing a pixel signal of an object;   color separating means for separating said pixel signal into first, second and third color pixel signals;   pixel signal processing means for passing through said first, second and third color pixel signals unchanged when a normal positive color image mode or a blue-back display of a negative image mode is selected by an operator and inverting said first, second and third color signals when a negative color image display mode or a blue-back display of a positive image mode is selected by an operator;   a matrix circuit for developing a luminance signal and first and second color difference signals from said first, second and third color pixel signals outputted by said pixel signal processing means;   comparator for comparing said luminance signal with a reference voltage and developing a comparison signal having a high logical value when said reference voltage is greater than said luminance signal and a low logical value when said reference voltage is less than said luminance signal;   blue-back processing means for passing through said luminance signal when said normal positive color image display mode and said negative color image display mode is selected by an operator and changing said luminance signal to a first predetermined voltage level and said second color difference signal to a second predetermined voltage level in response to said comparison signal being said high logical value, changing said luminance signal to a third predetermined voltage level and said second color difference signal to a fourth predetermined voltage level in response to said comparison signal being said low logical value with said first predetermined voltage level being greater than said third predetermined voltage level and said second predetermined voltage level being greater than said fourth predetermined voltage level and changing said first color difference signal to a fifth predetermined voltage level when said blue-back display of a positive image mode or a blue-back display of a negative image mode is selected by an operator; and   an encoder for developing a video signal from said luminance signal and said first and second color difference signals outputted by said blue-back processing means.   
     
     
       9. An image input device according to claim 8, wherein said image pickup means comprises an optical system for focusing on said object, a color image pickup device for reading out said pixel signal of said object in synchronism with a dot-sequence scanning timing by a predetermined drive and a pre-amplifier for amplifying said pixel signal from said color image pickup device. 
     
     
       10. An image input device according to claim 8, wherein said first color pixel signal comprises a red pixel signal, said second color pixel signal comprises a blue pixel signal and said third color pixel signal comprises a green pixel signal. 
     
     
       11. An image input device according to claim 10, wherein said first color difference signal comprises an R - Y color difference signal and said second color difference signal comprises an B - Y color difference signal. 
     
     
       12. An image input device according to claim 10, wherein said color image pickup device comprises a CCD solid state device. 
     
     
       13. An image input device according to claim 10, wherein said color image pickup device comprises a MOS solid state device. 
     
     
       14. An image input device according to claim 8, wherein said pixel signal processing means comprises first, second and third buffers for passing through said first, second and third color pixel signals respectively when said normal positive color image display mode or said blue-back display of a positive image mode is selected by an operator, first, second and third inverters for inverting said first, second and third color pixel signals respectively when said negative color image display mode or said blue-back display of a positive image mode is selected, first, second and third image reproduction switches for simultaneously switching between said normal positive and negative color image display modes and first, second and third γ correcting circuits for performing a γ correction on said first, second and third color pixel signals outputted from said first, second and third buffers or said first, second and third inverters respectively in response to said first, second and third image reproduction switches. 
     
     
       15. A method according to claim 14, wherein said first color pixel signal comprises a red pixel signal, said second color pixel signal comprises a blue pixel signal and said third color pixel signal comprises a green pixel signal. 
     
     
       16. A method according to claim 15, wherein said first color difference signal comprises an R - Y color difference signal and said second color difference signal comprises an B - Y color difference signal. 
     
     
       17. An image input device according to claim 8, wherein said blue-back processing means comprises first, second and third display mode switches for simultaneously switching said luminance and first and second color difference signals between said normal positive display color image mode and said negative color image display mode to said blue-back display of positive and negative modes and first and second voltage level switches for simultaneously switching between said first and second predetermined voltage levels and said third and fourth predetermined voltage levels in response to said comparison signal. 
     
     
       18. A method for reproducing negative and positive images of an object, comprising the steps of: (a) developing a pixel signal of the object by an image pickup device;   (b) separating said pixel signal into first, second and third color pixel signals;   (c) passing said first, second and third color pixel signals unchanged when a positive color image mode is selected by an operator;   (d) inverting said first, second and third color pixel signals when a negative color image mode is selected by an operator;   (e) developing a luminance signal and first and second color difference signals from said first, second and third color pixel signals outputted at said steps (c) and (d);   (f) passing said luminance and first and second color difference signals unchanged when a normal display mode is selected by an operator;   (g) inverting said luminance signal, changing said first color difference signal to a ground signal and changing said second color difference signal to a predetermined voltage signal when a blue-back display mode is selected by an operator; and   (h) developing a video signal from said luminance signal and said first and second color difference signals outputted at said steps (f) and (g).   
     
     
       19. A method according to claim 18, wherein said first color pixel signal comprises a red pixel signal, said second color pixel signal comprises a blue pixel signal and said third color pixel signal comprises a green pixel signal. 
     
     
       20. A method according to claim 19, wherein said first color difference signal comprises an R - Y color difference signal and said second color difference signal comprises an B - Y color difference signal. 
     
     
       21. A method for reproducing negative and positive images of an object, comprising the steps of: (a) developing a pixel signal of the object by an image pickup device;   (b) separating said pixel signal into first, second and third color pixel signals;   (c) passing said first, second and third color pixel signals unchanged when a positive color image is selected by an operator;   (d) inverting said first, second and third color pixel signals when a negative color image mode is selected by an operator;   (e) developing a luminance signal and first and second color difference signals from said first, second and third color pixel signals outputted at said steps (c) and (d);   (f) comparing said luminance signal with a reference voltage;   (g) developing a comparison signal having a high logical value when said reference voltage is greater than said luminance signal and a low logical value when said reference voltage is less than said luminance signal in response to the comparison at said step (f);   (h) passing said luminance and first and second color difference signals unchanged when a normal display mode is selected by an operator;   (i) changing said luminance signal to a first predetermined voltage level and said second color difference signal to a second predetermined voltage level in response to said comparison signal being said high logical value, changing said luminance signal to a third predetermined voltage level and said second color difference signal to a fourth predetermined voltage in response to said comparison signal being said low logical value with said first predetermined voltage level being greater than said third predetermined voltage level and said second predetermined voltage level being greater than said fourth predetermined voltage level and changing said first color difference signal to a fifth predetermined voltage level when a blue-back display mode is selected by an operator; and   (j) developing a video signal from said luminance signal and said first and second color difference signals outputted at said steps (h) and (i).